Draft head for waste wood burners



Nov. 18, 1958 R. E. HUFFSCHMIDT DRAFT HEAD FOR WASTE woon BURNERS Filed Jan. 21, 1955 INVENTOR. Z Z RoberfEHuffschmz'di United States Patent DRAFT HEAD FOR WASTE WOOD BURNERS Robert Edward Huifschrnidt, Portland, Oreg.,

Western Foundry Company, ration of Oregon assignor to Portland, Greg :1 corpo- This invention relates to a draft head for waste wood burners.

As is well known, the edgings, trimmings, slab wood, shavings, sawdust and other waste resulting from the operation of the conventional sawmill is conveyed at least in part to a refuse burner where it is disposed of by burning. To accommodate its bulky contents, the burner necessarily is of substantial dimensions, having in many installations a diameter of from 40 to 50 feet. Centrally located within the burner is a draft head provided with a multiplicity of ports through which air under pressure is fed to the burning wood. In the operation of such burners it is a primary problem to insure uniform and efficient combustion of the wood throughout the large volume of the burner, and to prevent rapid disintegration of the draft head because of the intense heat to which it is subjected.

Accordingly it is a primary object of the present invention to provide a draft head for waste Wood burners the use of which will effectuate the uniform and eflicient combustion of the wood throughout the burner.

It is another object of this invention to provide a draft head for waste wood burners which will have a long service life.

It is another object ofthis invention to provide a draft head for waste wood burners which is not made inoperative by'surface corrosion.

It is another object of this invention to provide a draft head for waste wood burners which feeds air uniformly to the burner despite cracking induced by thermal expansion.

It is another object of this invention to provide a draft head for waste wood burners which retains its shape in V use despite subjection to shock and cracking of its component parts.

It is another object of this invention to provide a draft head for waste wood burners which is easily and rapidly assembled and disassembled.

It is another object of this invention to provide a draft head for waste wood burners which is readily adaptable for use with the conventional refuse burners without substantial modification of the burner construction.

It is another object of this invention to provide a draft head for waste wood burners which has a remarkably high capacity and thereby correspondingly increases the capacity of a given saw mill.

It is another object of this invention to provide a draft head for waste wood burners the use of which minimizes or eliminates the smoke nuisance normally attending the operation of the burner.

The manner in which the foregoing and other objects of this invention are accomplished will be apparent from the accompanying specification and claims considered together with the drawing wherein like numerals indicate like parts and wherein:

Figure 1 is an elevational view partly broken away, of a waste wood burner including the presently described draft head;

r 2,860,625 Patented Nov. 18, 1958.

Figure 2 is a plan view of the draft head of the present invention;

Figure 3 is a view in side elevation of the draft head of Figure 2, partly in section better to show the interior construction;

Figure 4 is a sectional view taken along the lines 44 of Figure 3; and

Figure 5 is a sectional view taken along the line 5-5 of Figure 4.

As is indicated particularly in Figure 1 of the drawing, the draft head of this invention is adapted for use with a waste wood burner 10. Conventionally, this is a structure made of metal plates and having a bottom diameter of the order of 4050 feet. Its top portion comprises a spark arresting wire mesh dome 12. Conveying means 13 are provided for delivering the waste wood resulting from the manufacturing operation of the mill to the upper portion of the burner, where it is emptied into the interior.

The draft head indicated generally at 14 is centrally located at the bottom of the burner. It is connected through a pipe 16 with an air pump which supplies it with air as required to establish the desired draft within the burner.

The manner of application and construction of draft head 14 is apparent from Figures 2-5. It rests on a foundation member 18 within which is located a ring 20 for positioning and retaining pipe 16.

In the illustrated embodiment the draft head is comprised of four sections superimposed on each other. Three of these, i. e. the bottom section 22, the lower middle section 24, and the upper middle section 26 are in the form of hollow truncated cones which taper inwardly in an upward direction and are of progressively diminishing diameters. The top or dome section 28 likewise has tapered sides with the result that, when assembled, the four sections form a hollow body having a substantially cone shaped exterior configuration.

Spaced apart draft ports 29, 30, 31, 32 are provided at intervals throughout the body of the draft head. These preferably are directed downwardly to insure complete combustion of the waste wood on the floor of the burner.

The draft ports 29, 30, 31 in the bottom and middle sections preferably are located at their points of juncture with the next succeeding section of the assembly. This is for the reason that the passage of large volumes of air through the openings cools the meeting surfaces of the sections so that corrosion at these surfaces of the metal of which the sections are made is minimized.

Although the dimensions of the draft ports are somewhat variable, in aggregate they should be sufliciently large to accommodate and transmit the air capacity of pipe 16, thereby insuring the provision of an adequate draft within the burner.

Means are provided for releasably interconnecting the various sections of the draft head. Thus there are provided a plurality of bolt lugs 34, 36 adapted to receive bolts 38 at spaced intervals about the inner peripheries of the lower and lower middle sections. Similarly, about the inner peripheries of the lower middle and upper middle sections there are provided a plurality of spaced bolt lugs 49, 42. accommodating bolts 44 and offset the required amount to clear lugs 34, 36 and bolts 38..

Means also are employed for releasably interconnecting dome section 28 and upper middle section .26. Such means comprise in the illustrated form a plurality of lugs 46 extending downwardly and inclined outwardly from the lower inner edge of dome 28 at spaced apart intervals. Where the dome is superimposed upon the assembly, these lugs extend into clearance openings 48, associated with openings 31, so that they clear the inner sidewalls of section 26. It will be understood that if the vertical height of the draft openings 31 is increased from the dimension shown in Fig. 3 to be equal to or greater than the depending length of the lugs 46, the clearance openings 48 then are provided by the draft openings 31. Alternatiyely, ifthe lugs 46 are reduced in length to be equal to or less than the vertical height of the draft open ings 31 shown in Fig.1 3, then the clearance openings 48 neednot be provided. In any of these cases, the dome may then be rotated a fraction of a turn whereupon lugs 46 aremoved away from the clearance openings into a position in which they will engage the sidewalls of section 26 if removal ofthe dome is attempted.

Because of the intense temperature generated in the burner, the draft heads are subject to cracking because of thermal expansion. This weakens the structure and also opens up. large holes which disturb the draft pattern, causing uneven combustion. In the presently described draft head means are provided for controlling its cracking so that theseharmful result do not occur.

To this end the surfaces of the various sections comprising the draft head are scored or notched transversely at spaced intervals, preferably on both the inside and outside faces. Thus the exterior surface of lower section 22 is scored transversely with notches indicated by the numeral 50.. Similarly the exterior faces of the lower andupper middle sections, 24, 26 carry the transverse notches 52, 54 respectively. The inner faces of the sections may be notched correspondingly at the positions opposite the notches on the exterior face. This is indicated particularly in Figure 4, the interior notch 56 being opposite the exterior notch 54.

The notches in the various sections may or may not be aligned with each other, as desirable or necessary. In aggregate, they provide weakened areas of. the body which, upon being subjected to the stresses caused by thermal expansion and contraction, will break preferentially.

As a result, after a periodof use, the draft head may be composed of a plurality of fragments resulting from the fracture of the sections of which the head is composed. However, these fragments will be of substantially uniform size symmetrically arranged so that the draft head will retain its original configuration. Moreover, they are locked in this position in parts by bolts 33, 44, and lugs 46 and in part by means for linking them together at the points of fracture.

The linking means employed are illustrated particularly in Figures 4 and 5. As indicated, they comprise a plurality of spaced apart link members 58, 60 made of a relatively, durable material cast into the matrix comprising the body sections. Preferably they are shaped, in plan, in the form of butterflies, or double dovetails with the narrow section between the dovetails substantially opposite the exterior and interior surface grooves 54, 56. Accordingly as the sections of the draft head crack along the grooves, the resulting fragments will be linked together by the dovetailed link members which act as flaring tenons.

Furth rmore, it is to be observed that the inner horizontal dimension of the link members is substantially greater than the outer horizontal dimension. This provides a means for linking the fragments together even after; substantial exterior corrosion of the draft head occurs, Thus the exterior of the sections may be corroded away past the mid-point without the link members falling out, since they are retained in place by their long inner edges. This greatly prolongs the service life of the unit.

Henceit will be apparent that by the present invention I have provided a draft head which will distribute the air uniformly. over the area of the refuse burner, resulting in uniform combustion of the waste wood. The head is easily assembled and disassembled. Its service life is long, because even though it cracks as a consequence of thermal expansion and contraction, the resulting fragments. are. held together in a symmetrical form and the openings produced do not result in distortionof the draft 4 current. Furthermore, the fragments are held together in spite of severe exterior corrosion of the head.

It is to be understood that the form of my invention, herewith shown and described, is to be taken as a preferred example of the same, and that various changes in the shape, size and arrangement of parts may be re sorted to, without departing from the spirit of my invention, or the scope of the subjoined claims.

Having thus described my invention 1 claim:

1. A draft head for'waste wood burners comprising a plurality of sections superimposed upon each other to form a hollow body, and a plurality of draft ports through the body, the sections having transverse, spaced apart scorings across their respective faces to cause them to fracture along the scorings when thermally expanded.

2. A draft head for waste wood burners comprising a plurality of perforated sections superimposed upon each other to form a hollow body provided with draft ports therethrough, the sections having transverse spaced apart grooves across their respective faces to cause them to fracture along the grooves when thermally expanded, and a plurality of link members embedded in the sections opposite the grooves for linking together the pieces.

resulting from fracture along the grooves.

3. The draft head of claim 2 wherein the link members comprise elements which are substantially butterfly shaped in horizontal outline.

4. The draft head of claim 2 whereinthe link members are substantially Wider across the inner horizontal edge than across the outer horizontal edge, thereby form ing angular edges for retaining the link members after substantial corrosion of the outer surface of the draft head has occurred.

5. A draft head for wood waste burners comprising a plurality of hollow truncated cone sections of progressively smaller diameter superimposed upon each, other, a dome section superimposed on the truncated cone sections, the cone and dome sections formingwhen superimposed a. hollow draft head, a plurality, of, draft ports spaced apart at the juncture of each of the cone and dome sections with the section next adjacent, a plurality of lugs releasably interconnecting the dome section and the cone section adjacent thereto, and con. necting means interconnecting the cone sections with each other, the cone sections having a plurality of spaced apart transverse grooves in at least one of their. respective faces, the grooves acting upon thermal expansion. of the sections to insure their fracturing along the grooves, and imbedded in the cone section v opposite the grooves a plurality of link members adapted, upon fracture of the sections along the grooves, to interconnect the resulting fragments.

6. A draft head for waste burners comprising aplurality ofhollow truncated cone sections of progressively decreasing diameters superimposed upon each other with. the upper and lower transverse edges of adjacent cone sections lying in a single plane in abutment with each other, a dome section superimposed upon the uppermost cone section with the adjacent transverse edges lying in. a single plane in abutment with each other, thereby forming a hollow body, a plurality of spaced apart dl'flftl openings in said cone sections positioned at the upper transverse edges thereof, and apertured bolt lugs projecting inwardly from the inner surfaces of the cone sections, the apertured lugs on adjacent cone sections be ing capable of axial alignment in pairs for reception of bolts therethrough, whereby to secure said adjacent cone sections together, one of the lugs of each pair extending vertically across the plane ofsaid abutting transverse edges of adjacent cone sections whereby to form guide means for aligning the said adjacent cone sections axially.

7. A draft head for waste burners comprising ahollow. truncated cone section, a dome section superimposed upon the cone section with the adjacent transverseedgeslying in a single plane in abutment with each other thereby.

forming a hollow body, a plurality of spaced apart draft openings in the cone section positioned at the upper transverse edge thereof, the inner surface of the cone section converging upwardly, and a plurality of lugs on the dome section positioned for registration With the spaced draft openings in the cone section, the lugs extending downwardly and outwardly from the inner portion of the dome section and adapted preliminarily to project into said draft openings, and adapted ultimately upon rotation of said dome section to engage the inner surface of the cone section, whereby to secure said sections together.

8. A draft head for waste burners comprising a plurality of hollow truncated cone sections of progressively decreasing diameters superimposed upon each other with the upper and lower transverse edges of adjacent cone sections lying in a single plane in abutment with each other, a dome section superimposed upon the uppermost cone section with the adjacent transverse edges lying in a single plane in abutment with each other, the diameters of adjacent sections being proportioned to form a hollow body having a substantially continuous conical outer surface, a plurality of spaced apart draft openings through said body positioned at the edges of abutment of adjacent sections for cooling said edges during operation of the burner, the inner surface of the uppermost cone section section converging upwardly a plurality of lugs on the dome section positioned for registration with the spaced draft openings in the uppermost cone section, the lugs extending downwardly and outwardly from the inner portion of the dome section and adapted preliminarily to project into said draft openings, and adapted ultimately upon rotation of said dome section to engage the inner surface of the uppermost cone section, whereby to secure said sections together, and apertured bolt lugs projecting inwardly from the inner surfaces of the cone sections, the apertured lugs on adjacent cone sections being capable of axial alignment for reception of bolts therethrough, whereby to secure said adjacent cone sections together.

9. The draft head of claim 8 wherein the cone sections have a plurality of circumferentially spaced apart grooves formed longitudinally in at least one of their respective faces to cause them to fracture along said groove when thermally expanded, and a plurality of link members embedded in the cone sections opposite the grooves for linking together the pieces resulting from fracture along the grooves.

References Cited in the file of this patent UNITED STATES PATENTS 63,539 Low Apr. 2, 1867 426,847 Nogar Apr. 29, 1890 602,529 Van Buren Apr. 19, 1898 661,506 Fisher Nov. 13, 1900 1,360,250 Priebe Nov. 23, 1920 1,381,887 Rumereich June 14, 1921 1,889,548 Guay Nov. 29, 1932 2,185,028 Hoiland Dec. 26, 1939 FOREIGN PATENTS 12,458 Great Britain May 23, 1910 

